1. Field of Invention
This invention relates to a hooded respirator providing both high protection against toxic agents and compact storage.
2. Background of Invention
Utilization of an oral-nasal cup in combination with a neck-sealing hood is desirable for its protection factor and comfort to the wearer. However, when fashioning an apparatus that must be highly compacted, the presence of the oral-nasal cup poses a challenge because of its size and traditional configuration. Oral-nasal cups typically are fluidly coupled to one or more filters that purify incoming inhaled air. An important consideration in the design of a respiratory device is breathing resistance. A check valve, separate from the filter, discharges exhaled air. Preferably, the check valve is positioned in close proximity to the wearer""s face. This permits the exhaled air to take the shortest possible route before being discharged from the apparatus. In turn, this reduces the resistance encountered by the wearer during exhalation and thus lessens fatigue. Accordingly, oral-nasal cups typically have at least two separate fluid paths, one for exhalation and another for inhalation. The fluid paths each have a separate opening though the barrier that protects the wearer""s face.
A significant problem in the prior art is that of size. To be effective, the hooded respirator must be transported by military and civilian agencies and often donned with short notice. Accordingly, keeping the storage size small is an important factor in the deployment of a protective respiratory device. If the device is too large or cumbersome to transport, it will inhibit the individual""s ability to perform his or her task. Alternatively, the large size of the hooded respirator may even forgo the individual""s ability to carry potentially life-saving protection.
A possible solution is to fold the normally bulky oral-nasal cup during storage so that it takes up less room. However, in doing so, numerous problems arise. First, oral-nasal cups are biased against the face of the wearer to establish a substantially airtight seal. Therefore, the oral-nasal cup must be rigid enough not to collapse against the face under such pressure. However, a rigid oral-nasal cup cannot be effectively folded for storage. Soft, yielding material may be used for the oral-nasal cup so that folding is possible. However, when applied against the face, insufficient rigidity is provided by the material and the cup collapses against the face.
A second problem that arises in the compact storage of oral-nasal cups is that of anchor points. Oral-nasal cups normally have at least two conduits, one for inhalation and another for exhalation. If the device requires drink capability, then a third conduit may be present. Furthermore, many oral-nasal cup designs utilize two filters. Therefore, there may be four anchor points forming mechanical couplings on the oral-nasal cup. With multiple anchor points, it is not possible to effectively fold the oral-nasal cup into a compact shape. What is needed is a single anchor point to the oral-nasal cup to handle inhalation, exhalation, and drinking requirements. However, such a design is counterintuitive to the teachings of the prior art.
A third problem that arises in the compact storage of oral-nasal cups is that of cup distortion. As the interface between the cup and the face of the wearer is critical to maintaining a high protection factor, creasing of the oral-nasal cup as a result of folding may cause unfiltered air to be inhaled. Accordingly, there is substantial resistance by those skilled in the relevant art to fold the oral-nasal cup.
The present invention is a hooded respirator optimized for both high protection against nuclear, chemical and/or biological agents as well as having a design configuration enabling it to be stored as a highly compact unit. The hood includes a flexible, folding oral-nasal cup breathing interface interior to the hood. A mechanical filter-housing exterior to the hood is fluidly coupled by a single conduit that intakes filtered air during inhalation and exhaled air during exhalation. While flexible filters, integral to the hood, are known in the art, mechanical filters (filtration media encased in a substantially rigid enclosure) are considered more reliable and have greater capabilities.
When in storage, the flexible oral-nasal cup is folded into a substantially flat configuration. What makes this folding possible is that there is only a single conduit between the interior and exterior of the hood thereby providing a pathway for both inhalation and exhalation. The oral-nasal is secured by a single anchor point to the rest of the device. A drink tube is threaded through the single conduit. The drink tube permits the drinking of hot and cold liquids including liquid medication. Preferably, the diameter of the tube is sufficient to permit a drinking rate of at least 200 milliliters per minute.
The filter housing has a front side having at least one or more apertures for receiving unfiltered air. A rear side of the filter housing has the single conduit fluidly coupled to the breathing interface. The exhalation check valve is also positioned on the rear side of the filter housing. The filter housing interior holds particulate filtration media and carbon combination. Preferably, the particulate filter media and carbon combination provide protection against vapor, aerosol, and particulate matter threat agents. More specifically, the particulate filter media and carbon combination should protect again field concentrations of all military agents as defined in FM 3-9, all biological agents, radioactive fallout particles, and certain toxic industrial chemicals. Preferably, inhalation resistance through the filter media and into the oral-nasal should not exceed 30 mm of H2O when tested using a flow rate of 85 liters per minute.
An interior chamber coincident to the rear side of the filter housing is defined by a plurality of support ribs radiating from the single conduit. The support ribs serve at least three functions: (1) to define the interior chamber wherein inhaled and exhaled air is passed; (2) to direct inhaled air towards the single conduit from the filtration media; and (3) to direct exhaled air towards the exhalation check valve from the single conduit.
During inhalation, the support ribs direct inhaled, filtered air towards the single conduit to which they radiate. However, the support ribs must also direct exhaled air from the conduit to the exhalation check valve during exhalation. At least one or more passages are formed in the support ribs between the single conduit and the exhalation check valve to permit a flow of exhaled air. Therefore, during inhalation, the majority of airflow comprises a straight path through the filtration media and into the interior chamber. The flow then takes a ninety-degree turn and flows along the radiating support ribs to the single conduit where it takes another ninety-degree turn into the oral-nasal cup. During exhalation, airflow out of the oral-nasal cup through the single conduit takes a ninety-degree turn and flows down the interior chamber towards the exhalation check valve.
To minimize resistance, optimally, airflow strikes a check valve at a perpendicular angle. Positioning the exhalation check valve to accommodate this angle would necessitate the exhalation check valve being relocated to the bottom side of the filter housing, distal from the single conduit. However, in doing so, the package size of the filter housing would be unacceptably increased. The present inventors discovered that when exhaled air strikes the exhalation check valve, even a shallow angle, exhalation resistance is unexpectedly and dramatically reduced over that observed with a check valve angled parallel to air flow. Accordingly, in a preferred embodiment of the invention, the exhalation check valve in the interior chamber is canted towards the single conduit in a range between zero and ninety-degrees. Balancing both compact size and reduce breathing resistance, the angle is optimally eight-degrees. Exhalation resistance from the oral-nasal cup, through the single conduit and out the exhalation check valve should not exceed 20 mm H2O when tested using a flow rate of 85 liters per minute.
To enable the angled position of the exhalation check valve, the rear side of the filter housing may be arcuate. The heights of the support ribs vary in the interior chamber to offset the curve of the rear side of the filter housing. At least one exhalation conduit downstream from the exhalation check valve is provided, preferably with external baffles to inhibit the backflow of unfiltered air through the exhalation conduit. As noted above, airflow that strikes a check valve at a perpendicular angle generally provides the least amount of exhalation resistance. However, the present invention employs an angled exhalation check valve. Therefore, the portion of the exhalation check valve that tends to unseal first is that portion distal from the single conduit. Accordingly, it is preferred that the at least one exhalation conduit be positioned proximate to the portion of the exhalation check valve distal from the single conduit. A check valve cover sealingly covers the exhalation check valve and external baffles. The external baffles are defined by walls projecting from the rear side of the filter housing. The height of the walls varying in complementary relation to the arcuate slope of the rear side of the filter housing whereby the external baffle walls distal to the single conduit are higher than the external baffle walls proximate to the single conduit. Accordingly, a greater void exists between the check valve and the check valve cover distal to the single conduit. This greater void reduces air flow resistance along the optimum fluid path.
To form an acceptable seal about the face, the oral-nasal cup must be biased against the face of the wearer. Accordingly, a preferred embodiment of the invention includes at least one or more tension straps that encircle the head of the wearer. The tension straps are secured to the filter housing and adapted to bias the oral-nasal cup against the face of the wearer to form a substantially airtight seal. While the oral-nasal cup may be formed of various materials having differing elastomeric properties, the present invention anticipates a oral-nasal cup that can be folded over on itself during compact storage. This necessitates the utilization of a oral-nasal cup that is relatively soft and yielding. However, as the tension straps exert pressure on the filter housing, the oral-nasal cup may collapse. Accordingly, a preferred embodiment of the invention includes a pressure distribution bar secured to the filter housing and biased across a portion of the oral-nasal cup whereby force applied by the tension straps at the filter housing is distributed across the oral-nasal cup.
The respirator hood having the oral-nasal cup may be configured in a novel manner. A hood adapted to enclose the head of a wearer is provided, the hood having an interior and an exterior. A neck opening in the hood is provided, the neck opening adapted to seal about the neck of the wearer. A filter housing is provided, the filter housing adapted to filter inhaled air and exhaust exhaled air, the filter housing secured to the exterior of the hood. A flexible, resilient oral-nasal cup is secured to the interior of the hood, the cup having an upper portion covering the nose of the wearer when engaged and a contiguous lower portion covering the mouth of the wearer when engaged, an interior cavity wherein respiration occurs, an opening adapted to sealingly engage the wearer""s face and an exterior. An inwardly disposed lip about the perimeter of the cup is provided and the filter housing is fluidly coupled to the oral-nasal cup interior cavity through an aperture in the hood. The lip of the upper portion is pulled outward whereby it is fully extended. The upper portion and extended lip of the cup are folded to lay flat against the lower portion of the cup across a fold line defined by the cup opening. Finally, the cup is then pulled through the neck opening.
For a fuller understanding of the nature and objects of the invention, reference should be made to the following detailed description, taken in connection with the accompanying drawings, in which:
FIG. 1 is a perspective view of the rear side of the filter housing with the check valve cover removed.
FIG. 2 is a perspective of the interior chamber of the filter housing showing the support ribs radiating from the single conduit.
FIG. 3 is an elevated, isometric view of the oral-nasal cup fluidly coupled to the filter housing without the hood installed.
FIG. 4 is an elevated, isometric view of the upper portion of the oral-nasal cup folded down to lay coincident to the lower portion of the oral-nasal cup across a fold line defined by the oral-nasal cup opening.
FIG. 5 is top elevated view of the filter housing secured to a cross section of the hood.
FIG. 6 is an elevated, isometric view of the rear side of the filter housing relative to the position of the hood.
FIG. 7 is an isometric, exploded view of the filter housing components.
FIG. 8 is an isometric, exploded view of the filter housing components.
FIG. 9 is an isometric, exploded view of the filter housing components.
FIG. 10 is an elevated view of the interior of the oral-nasal cup.
FIG. 11 is an isometric view of the oral-nasal cup prior to folding.
FIG. 12 is an isometric view of the oral-nasal cup with the lower portion of the cup folded down.
FIG. 13 is an isometric view of the oral-nasal cup with the lip of the upper portion pulled out and folded flat against the lower portion of the cup.
FIG. 14 is an elevated view of the oral-nasal cup in a folded configuration.
FIG. 15 is an elevated view of the oral-nasal cup in an intermediary unfolded configuration.
FIG. 16 is an elevated view of the oral-nasal cup fully unfolded.
FIG. 17 is an elevated view of the oral-nasal cup after storage in a folded configuration.